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I'm building a touch screen kiosk using an iPad and a USB BarCode Scanner (through the camera connection kit).

the problem:

The pinout here shows the USB pin that the scanner would connect to. However it appears that the charger (info here) also requires the D+ D- Pins to initiate charging.

How can I charge the iPad at the same time as the Bar Code Scanner being used? In theory, this should be possible since iPhone/iPad do charge (however slow) while connected to a PC.

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  • \$\begingroup\$ Is it possible to do from a hardware perspective ? Probably. However, the iPad software may not support it. It's likely you would have to alter the software on the PMIC in the iPad, which is (basically) impossible. \$\endgroup\$ Commented Apr 19, 2012 at 0:47
  • \$\begingroup\$ How is the barcode scanner powered? It doesn't seem that the iPad could provide power out to the scanner while simultaneously accepting power in to recharge, on the same pins, regardless of other configuration issues like the pullup/down resistors mentioned in the link. \$\endgroup\$
    – Matt B.
    Commented Apr 19, 2012 at 7:09
  • \$\begingroup\$ The iPad can already scan barcodes with the camera, that's how RedLaser (app) does it. Do you really need a hardware barcode scanner? \$\endgroup\$
    – Matt B.
    Commented Apr 19, 2012 at 7:12
  • \$\begingroup\$ @Matt B, the scanner can be powered 5V separately. A will have to, since the iPad can't supply the current it needs. The camera barcode reader wouldn't work reliably in this case. \$\endgroup\$
    – MandoMando
    Commented Apr 19, 2012 at 13:32
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    \$\begingroup\$ It's not clear that the resistor pullup/downs get in the way of data communication, since the lines could be left floating for however long is required to read the analog voltage before treating the lines as digital. However, a USB port is supposed to be either host or slave, not both at the same time. If the iPad is host to the scanner data-wise, the iPad probably won't take power (charging) input on the same port at the same time. At least not without some trickery...perhaps by experimenting you could make it work. \$\endgroup\$
    – Matt B.
    Commented Apr 20, 2012 at 5:07

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I haven't yet verified this with the MFi documentation. However, it sounds like Matt B. is correct in the sense that you can't be both a USB host and a USB client at the same time and charging means you're acting as a client so host functionality should stop.

Other pins such as iPod controls, audio, video, etc may remain operable still which charging since they don't use USB.

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